How do I run a funsuite test within a for loop? - scala

I am very new to scala so trying to understand how funsuite testing works. I have a bunch of tests that take a method data() to set it as a particular method from a variety of methods namely method1(): Long, method2(): Long etc
I figured defining the method1/2/... etc within the class would be fine and then sequentially go through them for my tests rather than having to write duplicate tests for each method, but seems like the data cannot be found by the tests. I also tried putting both the tests inside the for loop but then I am having issues with the IDE not being able to find tests. What am I doing wrong?
Example
class controlTest extends Anyfunsuite {
protected def method1(): Long = { a() }
protected def method2(): Long = { b() }
protected def method3(): Long = { c() }
for(i <- Seq(method1(), method2(), method3()) {
def data(): Long = i
}
test("testing1"){
data()
....
}
test("testing2"){
data()
...
}

Related

Mockito-Mock functions within scala object for unit testing

I have a few functions within a scala object. The functions internally call other functions of the same object.
object A {
def method1:Unit= {
spark=CreateSparkSession.create()
Method2(spark,dbnm)
}
def Method2(spark:Sparksession, dbnm:String):Unit= {
//some implementation
}
}
How can I write Unit testcase for Method1 without actually invoking method2.
CreateSparksession is another object with create method that returns sparksession.
You cannot mock methods in an object. And you should not mock methods in class that you are testing (if it looks like you need to, it is a definite symptom of violating the single responsibility principle).
What you can do is something like this:
trait Api1 {
def method1(
...
): Unit // NB: also, should not really return a Unit: how are you going to test this???
}
trait Api2 {
def method2(...): Unit // See above
}
class Impl2 extends Api2 {
def method2(...) = // Do stuff
}
class Impl1(val api2: Api2) extends Api1 {
def method1(...) = { ... ; api2.method2(); ... }
}
// You should not really need this, but, you can have it if you want
object A extends Impl1(new Impl2)
So, now testing this code is trivial:
describe("Impl2") {
it ("does nothing") {
new Impl2().method2("foo")
// Nothing happens
// this is what I meant: how do you know it worked?
}
}
describe("Impl1") {
it ("does nothinig") {
val a2 = mock[Api2]
doNothing when a2 method2(any)
val fixture = new Impl1(a2)
fixture.method1()
// Again, nothing happens!
verify(a2).nothing("foo")
}

scala - mock function and replace implementation in tests

I'm using scalatest and when I test my code, I want to replace an implementation of a function to return something else when running tests.
In JavaScript its really simple and I thought I could do the same in scala.
So what I want is something like this:
object Module {
private def bar(): Int = {
5
}
def foo(): Unit = {
println(bar())
}
}
And the test will be something like that (dont mind the syntax, you get the idea)
class Test extends FunSpec {
mock(Module.bar, () => 1)
describe("Test") {
it("Test") {
Module.foo() // will print 1
}
}
}
I have searched the internet and came across scala mock libraries but none of them seemed to be able to replace the implementation of a method.
In every library you have to defined your mock in the test and pass it on to the code, but I don't want to do that.
Is there anyway to achieve this?
Thank you.
You can't mock Object in Scala, because it's like a static class in java (which you can't mock either). (and you can't mock scala objects not in mockito nor scalamock (maybe in their next version)).
But, if you change your object Module to class Module, you can mock this function easily (using mockito):
val mockModule = mock[Module]
when(mockModule.bar()).thenReturn(1)
You can do a fake class that has that function and put the value you want, if you dont want to use mocks, like this:
trait SMT{
def bar: Int
}
class RealImpl extends SMT{
def bar: Int = 5
}
class FakeImpl extends SMT{
def bar: Int = 1
}

How To Create Temporary Directory in Scala Unit Tests

In scala how can a unit test create a temporary directory to use as part of the testing?
I am trying to unit test a class which depends on a directory
class UsesDirectory(directory : java.io.File) {
...
}
I'm looking for something of the form:
class UsesDirectorySpec extends FlatSpec {
val tempDir = ??? //missing piece
val usesDirectory = UsesDirectory(tempDir)
"UsesDirectory" should {
...
}
}
Also, any comments/suggestions on appropriately cleaning up the resource after the unit testing is completed would be helpful.
Thank you in advance for your consideration and response.
Krzysztof's answer provides a good strategy for avoiding the need for temp directories in your tests altogether.
However if you do need UsesDirectory to work with real files, you can do something like the following to create a temporary directory:
import java.nio.file.Files
val tempDir = Files.createTempDirectory("some-prefix").toFile
Regarding cleanup, you could use the JVM shutdown hook mechanism to delete your temp files.
(java.io.File does provide deleteOnExit() method but it doesn't work on non-empty directories)
You could implement a custom shutdown hook using sys.addShutdownHook {}, and use Files.walk or Files.walkTree to delete the contents of your temp directory.
Also you may want to take a look at the better-files library, which provides a less verbose scala API for common files operations including File.newTemporaryDirectory() and file.walk()
File in Java is very cumbersome to test. There is no simple way to create some kind of virtual filesystem abstraction, which can be used for tests.
A cool way around it is to create some kind of wrapper, that can be used for stubbing and mocking.
For example:
trait FileOps { //trait which works as proxy for file
def getName(): String
def exists(): Boolean
}
object FileOps {
class FileOpsImpl(file: File) extends FileOps {
override def getName(): String = file.getName //delegate all methods you need
override def exists(): Boolean = file.exists()
}
implicit class FromFile(file: File) { //implicit method to convert File to FileOps
def toFileOps: FileOpsImpl = new FileOpsImpl(file)
}
}
Then you'd have to use it instead of File in your class:
class UsesDirectory(directory : FileOps) {
...
}
//maybe you can even create implicit conversion, but it's better to do it explicitly
val directory = new UserDirectory(file.toFileOps)
And what is benefit of that?
In your tests you can provide custom implementation of FileOps:
class UsesDirectorySpec extends FlatSpec {
val dummyFileOps = new FileOps {
override def getName(): String = "mock"
override def exists(): Boolean = true
}
//OR
val mockFileOps = mock[FileOps] //you can mock it easily since it's only trait
val usesDirectory = UsesDirectory(dummyFileOps)
"UsesDirectory" should {
...
}
}
If you use this or a similar approach, you don't even need to touch filesystem in your unit test.

Scala Mockito Guice and Partial Mocking .... methods get called twice

I have the following code written in Scala, Guice, Mockito and ScalaTest
import javax.inject.Singleton
import com.google.inject.Inject
#Singleton
class TestPartialMock #Inject()(t1: Test1, t2: Test2) {
def test3() = "I do test3"
def workHorse() : List[String] = {
println("+++++ came inside ++++++++")
List(t1.test1(), t2.test2(), test3())
}
}
class MainModule extends ScalaModule {
override def configure() = {
bind[Test1]
bind[Test2]
bind[TestPartialMock]
}
}
and I have written unit test cases with partial mocking
class PartialMockTest extends FunSpec with Matchers {
describe("we are testing workhorse but mock test3") {
it("should return mock for test3") {
val module = new TestModule
val injector = Guice.createInjector(module)
val tpm = injector.getInstance(classOf[TestPartialMock])
val result = tpm.workHorse()
result should contain ("i do test2")
result should contain ("i do test1")
result should contain ("I am mocked")
result should not contain ("I do test3")
}
}
}
class TestModule extends AbstractModule with ScalaModule with MockitoSugar {
override def configure() = {
val module = new MainModule()
val injector = Guice.createInjector(module)
val realobject = injector.getInstance(classOf[TestPartialMock])
val x = spy(realobject)
when(x.test3()).thenReturn("I am mocked")
when(x.workHorse()).thenCallRealMethod()
bind(classOf[TestPartialMock]).toInstance(x)
}
}
My tests are successful and I can see that it mocks the right set of methods and calls the actual implementation of the right set of methods. BUT when I look at the output I see
info] Compiling 5 Scala sources to /Users/IdeaProjects/GuicePartialMock/target/scala-2.12/classes...
[info] Compiling 1 Scala source to /Users/IdeaProjects/GuicePartialMock/target/scala-2.12/test-classes...
+++++ came inside ++++++++
+++++ came inside ++++++++
[info] PartialMockTest:
[info] we are testing workhorse but mock test3
[info] - should return mock for test3
[info] Run completed in 2 seconds, 92 milliseconds.
Why am I seeing the print statement came inside twice?
Edit::
Based on advice of Tavian ... this is the final code which worked
class TestModule extends AbstractModule with ScalaModule with MockitoSugar {
override def configure() = {
val module = new MainModule()
val injector = Guice.createInjector(module)
val realobject = injector.getInstance(classOf[TestPartialMock])
val x = spy(realobject)
when(x.test3()).thenReturn("I am mocked")
bind(classOf[TestPartialMock]).toInstance(x)
}
}
For spies, you need to be careful of expressions like
when(x.workHorse()).thenCallRealMethod()
because x.workHorse() really is invoked in this expression! x doesn't "know" that it's inside a when() call, as the expression is lowered into something like this:
tmp1 = x.workHorse();
tmp2 = when(tmp1);
tmp3 = tmp2.thenCallRealMethod();
Instead, you can write
doCallRealMethod().when(x).workHorse()
which will suppress the invocation of the real workHorse() implementation.
But, you don't need to do any of this for this example—calling real methods is the default behaviour of spies.
As you mentioned in the question title, you have a combination of 3 technologies. Actually 4 technologies including build tool that is used to run the test. You can isolate the problem by
1) Remove Guice and instantiate everything directly
2) Run code as a simple App instead of running as a test by sbt/gradle/maven.
Also it makes sense to print stack trace together with a came inside message to find a caller.

Is it possible to mock a function that is defined within another function?

I have some functions that access a database, which I need to mock for testing purposes.
For ease of use, I would like to define these functions within another function, where I can leverage scope to reduce the number of arguments I have to pass.
I need to test the parent function, while mocking the nested functions.
Are there any tricks to mock functions that are nested?
As a secondary question, are there ways to mock functions when nested at arbitrary depth?
And a side note: my project is light enough I'm not even using classical mocking, just stackable traits like this blog post suggests; but for this question, any kind of mocking is fine.
Here is some very simple example code:
class Storage {
def storeData(specId: Long, data: String): Unit = {
val rawPath = "/path/to/file"
def storeFsEntry: Unit = {
// do stuff
}
def storeDbEntry: Unit = {
// do stuff we need mocked
}
if ( specId == 1 )
{
storeDbEntry
storeFsEntry
}
}
}
It's not possible, but you can define a trait and implement it inside your function (if you really want this logic been implemented inside):
class Storage {
trait Storing {
def path: String //you have to define all free members
def storeDbEntry: Unit
def storeFsEntry: Unit
}
def storeData(specId: Long, data: String, storingDefault: Option[Storing] = None): Unit = {
val myStoring = new Storing {
...implement it here
}
val storing = storingDefault getOrElse myStoring
import storing._
if ( specId == 1 ) {
storeDbEntry
storeFsEntry
}
}
}
Your mock will be something like that:
trait StorageMock extends Storage {
override def storeData(specId: Long, data: String, storingDefault: Option[Storing] = None): Unit = {
val storingOverride = new Storing { ... } //mocking functionality
super.storeData(specId, data, storingDefault orElse Some(storingOverride))
}
}
new Storage with StorageMock
You may also turn storingDefault into a member instead of function parameter.
The reason why it's not possible to do same for inner functions is that they are private and also typecheck can't be performed on them (in comparison with inner traits).